This page shows what was measured, who it was measured in, and what that does not settle.
What Voxelotor does in the body
Nonclinical studies suggest that voxelotor may inhibit RBC sickling, improve RBC deformability, and reduce whole blood viscosity.
From the FDA-approved label: Voxelotor is a hemoglobin S (HbS) polymerization inhibitor that binds to HbS with a 1:1 stoichiometry and exhibits preferential partitioning to red blood cells (RBCs). By increasing the affinity of Hb for oxygen, voxelotor demonstrates dose-dependent inhibition of HbS polymerization.
Why people take it. Sickle cell disease
What happened in people
RNAWiki has not yet published a reviewed conclusion for this use.
§ A fixed RNAWiki sentence
Where this came from
Wording RNAWiki always uses, not a finding about this substance.
No reviewed claim names a result for any goal on this record.
No source is stored against this line.
The limit that matters most
Not recorded.
Where it acts
Not recorded.
Kind of result
No result is published, so no kind of result applies yet
Supervision
Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.
What the registries record it as
The substance registry classes this as chemical.
FDA substance registry · 3ZO554A4Q8 · read 2026-08-29
Its recorded molecular formula is C19H19N3O3, weighing 337.4.
US prescribing information · 3c557fac-29ec-483f-b691-8a935d4decc3 · read 2026-08-30
Where each sentence above came from
A person wrote this explanation into the record, with the studies named in the path below.
The recorded use, written for a reader without medical training. Not signed off.
No statement of the main limit is recorded.
The four opening statements run to 76 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Biomarker
A biomarker is a number from a test that stands in for something about health.
A picture of it, and where the picture fails
A biomarker is like a fuel gauge.
Where that stops being true. A gauge is wired to the tank. Many biomarkers are only loosely tied to health.
What people get wrong. A better number is read as a better life. Several medicines improved a number and helped nobody.
A measurable indicator used as a substitute for a clinical outcome of interest.
Placebo
A placebo is a dummy treatment given so the real one can be compared with it.
A picture of it, and where the picture fails
A placebo is like a blank control in an experiment.
Where that stops being true. A blank does nothing. People given a placebo often do get better.
What people get wrong. A placebo effect is read as imaginary. The improvement is measured and real.
An inactive intervention matched in appearance to the test intervention, used to control for non-specific effects.
Comparator
A comparator is whatever the treatment was measured against.
A picture of it, and where the picture fails
It is like the other runner in a race.
Where that stops being true. A race has one winner. A study can show both arms improved.
What people get wrong. Results are read without asking what the other group got. Beating nothing is not beating a treatment.
The control condition against which the experimental intervention is assessed.
What happened in people◇Read from sources, not yet reviewed
What happened in people
Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.
Number of Participants With Increase in Hb >1 g/dL From Baseline to Week 24
✗ The study did not show it
Who was studied
NCT03036813
How many people
449
Study design
Phase 3
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. No limitation is recorded for this study.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
openFDA Drugs@FDA · a recorded source, not a stored snapshot
openFDA NDC Directory · a recorded source, not a stored snapshot
openFDA SPL label · a recorded source, not a stored snapshot
PubChem PUG-REST · a recorded source, not a stored snapshot
Annualized rate of VOCs that are healthcare professional (HCP)-managed (including VOCs leading to management at a health care facility or those managed via remote consultation) in each treatment arm
✗ The study did not show it
Who was studied
NCT06439082
How many people
354
Study design
Phase 3
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. No limitation is recorded for this study.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
openFDA Drugs@FDA · a recorded source, not a stored snapshot
openFDA NDC Directory · a recorded source, not a stored snapshot
openFDA SPL label · a recorded source, not a stored snapshot
PubChem PUG-REST · a recorded source, not a stored snapshot
Annualized Rate of Vaso-occlusive Crisis (VOC) Events Leading to a Healthcare Visit
✗ The study did not show it
Who was studied
NCT03814746
How many people
254
Study design
Phase 3
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. No limitation is recorded for this study.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
openFDA Drugs@FDA · a recorded source, not a stored snapshot
openFDA NDC Directory · a recorded source, not a stored snapshot
openFDA SPL label · a recorded source, not a stored snapshot
PubChem PUG-REST · a recorded source, not a stored snapshot
Change From Baseline in Time-Averaged Maximum of Mean Velocity (TAMMV) Arterial Cerebral Blood Flow at Week 24
✗ The study did not show it
Who was studied
NCT04218084
How many people
236
Study design
Phase 3
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. No limitation is recorded for this study.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
openFDA Drugs@FDA · a recorded source, not a stored snapshot
openFDA NDC Directory · a recorded source, not a stored snapshot
openFDA SPL label · a recorded source, not a stored snapshot
PubChem PUG-REST · a recorded source, not a stored snapshot
Number of Participants With Sickle Cell Disease (SCD)-Related Treatment Emergent Adverse Events (TEAEs)
✗ The study did not show it
Who was studied
NCT03573882
How many people
179
Study design
Phase 3
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. No limitation is recorded for this study.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
openFDA Drugs@FDA · a recorded source, not a stored snapshot
openFDA NDC Directory · a recorded source, not a stored snapshot
openFDA SPL label · a recorded source, not a stored snapshot
PubChem PUG-REST · a recorded source, not a stored snapshot
Number of Participants With Treatment Emergent Adverse Events (AEs)
✗ The study did not show it
Who was studied
NCT04188509
How many people
162
Study design
Phase 3
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. No limitation is recorded for this study.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
openFDA Drugs@FDA · a recorded source, not a stored snapshot
openFDA NDC Directory · a recorded source, not a stored snapshot
openFDA SPL label · a recorded source, not a stored snapshot
PubChem PUG-REST · a recorded source, not a stored snapshot
What we know
RNAWiki holds 6 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
OXBRYTA is indicated for the treatment of sickle cell disease (SCD) in adults and pediatric patients 4 years of age and older. This indication is approved under accelerated approval based on increase in hemoglobin (Hb) [see Clinical Studies (14) ]. Continued approval for this indication may be contingent upon verification and description of clinical benefit in confirmatory trial(s).
Who is missing from the studies
Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What the label states about particular groups
On pediatric, the label states: “The safety and efficacy of OXBRYTA in pediatric patients with SCD below the age of 4 years have not been established.”
US prescribing information · 3c557fac-29ec-483f-b691-8a935d4decc3 · read 2026-08-30
On older people, the label states: “Clinical studies of OXBRYTA did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.”
US prescribing information · 3c557fac-29ec-483f-b691-8a935d4decc3 · read 2026-08-30
On people who are pregnant, the label states: “Risk Summary There are no available data on OXBRYTA use in pregnant women to evaluate for a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes.”
US prescribing information · 3c557fac-29ec-483f-b691-8a935d4decc3 · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary There are no data on the presence of voxelotor in human milk, the effects on the breastfed child, or the effects on milk production.”
US prescribing information · 3c557fac-29ec-483f-b691-8a935d4decc3 · read 2026-08-30
On people with reduced liver function, the label states: “Severe hepatic impairment increases voxelotor exposures [see Clinical Pharmacology (12.3) ] .”
US prescribing information · 3c557fac-29ec-483f-b691-8a935d4decc3 · read 2026-08-30
Where the result stopped carrying
This is a scope explorer, not a diagnosis engine.
It shows who was studied so you can see whether people similar to you were included.
RNAWiki cannot tell whether a study fits you. It can show who was in it.
What it would be like to take◇Read from sources, not yet reviewed
Why it might seem to do nothing
A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.
It was studied in different people
The people in the studies were not much like the reader.
On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
The evidence may simply be wrong
Small early studies often do not hold up.
On this record: RNAWiki has not yet published a reviewed conclusion for this use.
Other reasons RNAWiki checked and found nothing for (11)
It was studied for a different goal
The studies measured something else entirely. Nothing in this record points to this reason.
A different form was studied
The studied form is not the form on the shelf. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
The change is too small to feel
A real change can still sit below what a person notices. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
The product may not be what it says
Contents of a sold product are not always what the label states. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.
None of these is a reason to take more. Taking more is not a step this page ever suggests.
What it would be like to take◇Read from sources, not yet reviewed
What taking it involves
The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.
How it is supplied
Withdrawn
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
Oral
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Suppression classes recorded: S8.
No source is stored against this line.
What is in the pack
Sold as tablet, tablet, for suspension, tablet, film coated, given by the oral route.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold and what that means for what is in the pack.
No source is stored against this line.
Where it is registered
Regulatory records are listed in the technical disclosure at the foot of this page.
# Counted from records
Where this came from
A count of rows RNAWiki holds. It describes our records, not your body.
Register entries are stored per jurisdiction and shown with their dates.
No source is stored against this line.
Why people stop
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No record of why people stopped taking it is stored for this substance.
No source is stored against this line.
What it would be like to take∅Nothing found in the sources checked
What can go wrong
Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.
∅Nothing found in the sources checked
No harm is recorded against this substance in the sources RNAWiki checked. Finding nothing is not the same as showing there is nothing.
The sources listed were searched and held nothing. That is not the same as nothing existing.
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear◇Read from sources, not yet reviewed
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Oral
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
Nothing further is recorded about which forms are sold.
No source is stored against this line.
What is recorded as being sold
12 products list this as an active ingredient in the United States drug directory. 12 of them contain it and nothing else.
FDA National Drug Code directory · 66406-0301 · read 2026-08-29
They are sold as powder, tablet, film coated and tablet, for suspension, taken oral.
FDA National Drug Code directory · 66406-0301 · read 2026-08-29
The regulator's established pharmacologic class for it is cytochrome p450 3a4 inhibitors [moa], hemoglobin s polymerization inhibitor [epc] and hemoglobin s polymerization inhibitors [moa].
FDA National Drug Code directory · 66406-0301 · read 2026-08-29
1 published label names it as an active ingredient. 1 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · 3c557fac-29ec-483f-b691-8a935d4decc3 · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · 3c557fac-29ec-483f-b691-8a935d4decc3 · read 2026-08-29
OXBRYTA is oral at 3 DOSAGE FORMS AND STRENGTHS Tablets: 300 mg light purple to purple, oval shaped, biconvex, debossed with "G 300" on one side., recorded as fda label in effect 2023-12-26 in the United States.
US prescribing information · 3c557fac-29ec-483f-b691-8a935d4decc3 · read 2026-08-30
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
Self-experiment planning is not offered for a prescription or clinician-supervised medicine, withdrawn medicine. The questions below are for a clinician or pharmacist.
Questions worth asking
Which of the trials of Voxelotor studied people like me?
What was measured, and for how long?
Was the result a laboratory value or a health outcome?
What would we watch for, and when would we stop?
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki records evidence. It does not say whether this substance is right for you.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Voxelotor are recorded. Results from one form may not transfer to another.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Mechanism not reviewed
No reviewed mechanism story exists for this substance.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
What happened in people◇Read from sources, not yet reviewed
Check any of this yourself
Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.
Where else this substance is registered
FDA substance identifier (UNII)
3ZO554A4Q8
RxNorm concept
2265683
Checks this page had to pass
✓ Passed
Identity resolved
no open identity hold
✓ Passed
No unresolved merge across substance families
no quarantine open
✓ Passed
Every public sentence names a source
The opening statement carries the origin: Written into the record, not signed off.
✗ Not passed
Trial roles classified for highlighted evidence
No registered study is classified as testing this substance.
✓ Passed
No internal keys in reader text
enforced by the copy-contract test over the rendered page
✓ Passed
Safety mode resolved
Suppression classes recorded: S8.
✓ Passed
Canonical metadata present
slug and display name present
What is missing or unclear◇Read from sources, not yet reviewed
How this medicine reached us
Kept near the foot of the page. A historical event moves up only when it changes something about this substance today.
Withdrawn in United Kingdom; European Union; United States, 2024, for "higher rate of vaso-occlusive crisis (severe pain caused by sickled red blood cells blocking blood flow and oxygen delivery to tissues) in patients with sickle cell disease receiving Oxbryta compared…" (ChEMBL; Open Targets)
Withdrawn in United Kingdom; European Union; United States, 2024, for "vascular toxicity" (ChEMBL; Open Targets)
Withdrawn in United Kingdom; European Union; United States, 2024, for "unfavourable imbalance in the number of vaso-occlusive crises and fatal events" (ChEMBL; Open Targets)
Withdrawn in United Kingdom; European Union; United States, 2024, for "higher occurrence of vaso-occlusive crises (VOC) during treatment. Higher number of deaths" (ChEMBL; Open Targets)
What the approval register records
2 approved applications cover products containing this substance. The earliest was NDA213137, approved 20191125 to GLOBAL BLOOD THERAPS.
This order is fixed in code and does not count clicks or time on the page.
What is not here
9 questions this page could not answer
These sections were prepared and left out because there was nothing to put in them. They are listed rather than hidden, so the gaps in this record are visible.
What was measured, goal by goal — found nothing in the sources checked.
How close this is to real life — found nothing in the sources checked.
The path through the body — found nothing in the sources checked.
Felt, measured, or meaningful — found nothing in the sources checked.
How long anything takes — found nothing in the sources checked.
What it may clash with — found nothing in the sources checked.
Other ways to the same goal — found nothing in the sources checked.
Claims that go past the evidence — found nothing in the sources checked.
What changed on this page — found nothing in the sources checked.
The record as stored
The full record, for auditing
Everything above is built from what is below. This layer keeps the technical vocabulary, record identifiers and every stored row, so a reader who wants to check the page can.
Recorded evidence blocks (12)
Q2
On the Voxelotor label: indicated for what?
"OXBRYTA is indicated for the treatment of sickle cell disease (SCD) in adults and pediatric patients 4 years of age and older. This indication is approved under accelerated approval based on increase in hemoglobin (Hb) [see Clinical Studies (14) ] .": indications and usage on Voxelotor's label. DailyMed label · 3c557fac-29ec-483f-b691-8a935d4decc3 · 2023-12-26
Q3
19 registered trials of Voxelotor — at which phases?
Approved in 2019, withdrawn in 2024: what happened to Voxelotor in European Union and United Kingdom; European Union; United States?
Approved 2019, withdrawn 2024 in European Union and United Kingdom; European Union; United States; the register's words: "higher rate of vaso-occlusive crisis (severe pain caused by sickled red blood cells blocking blood flow and oxygen delivery to tissues) in patients with sickle cell disease receiving Oxbryta compared to placebo. There were also more deaths". Open Targets drug warning · CHEMBL4101807 · 2026-06-24
8 recorded reasons; European Union, United Kingdom; European Union; United States
Show the evidence
Reason
"higher rate of vaso-occlusive crisis (severe pain caused by sickled red blood cells blocking blood flow and oxygen delivery to tissues) in patients with sickle cell disease receiving Oxbryta compared to placebo. There were also more deaths"
"vascular toxicity"
"unfavourable imbalance in the number of vaso-occlusive crises and fatal events"
"higher occurrence of vaso-occlusive crises (VOC) during treatment. Higher number of deaths"
"higher occurrence of vaso-occlusive crises (VOC) during treatment. Higher number of deaths"
"higher rate of vaso-occlusive crisis (severe pain caused by sickled red blood cells blocking blood flow and oxygen delivery to tissues) in patients with sickle cell disease receiving Oxbryta compared to placebo. There were also more deaths"
2 more recorded rows
Reason
"vascular toxicity"
Reason
"unfavourable imbalance in the number of vaso-occlusive crises and fatal events"
recorded 2026-06-24 · last checked 2026-09-04
Q5
11 of Voxelotor's trials stopped: safety, funding/business, other?
"Emerging clinical data evaluated by Pfizer and shared with regulatory authorities indicates that the risk profile of voxelotor in people with SCD exceeds the benefits observed in previously generated global research and requires further assessment."; 11 of 19 registered studies
Show the evidence
Trial
NCT02850406
terminated; "Emerging clinical data evaluated by Pfizer and shared with regulatory authorities indicates that the risk profile of voxelotor in people with SCD exceeds the benefits observed in previously generated global research and requires further…"
NCT03573882
terminated; "Emerging clinical data evaluated by Pfizer and shared with regulatory authorities indicates that the risk profile of voxelotor in people with SCD exceeds the benefits observed in previously generated global research and requires further…"
NCT04188509
terminated; "Emerging clinical data evaluated by Pfizer and shared with regulatory authorities indicates that the risk profile of voxelotor in people with SCD exceeds the benefits observed in previously generated global research and requires further…"
NCT04218084
terminated; "Emerging clinical data evaluated by Pfizer and shared with regulatory authorities indicates that the risk profile of voxelotor in people with SCD exceeds the benefits observed in previously generated global research and requires further…"
NCT04247594
terminated; "Data will not inform further development of Voxelotor"
NCT04335721
terminated; "Sponsor voluntarily suspended distribution and removed product from the market"
5 further recorded trials
NCT04930445
terminated; "Emerging clinical data evaluated by Pfizer and shared with regulatory authorities indicates that the risk profile of voxelotor in people with SCD exceeds the benefits observed in previously generated global research, and requires further…"
NCT05018728
terminated; "This study was terminated on September 26, 2024 due to voluntary withdrawal of study drug from the market."
NCT05228821
withdrawn; "The study has been stopped due to Sponsor's business reasons. The termination is not a result of any safety concerns or change in the benefit-risk ratio."
NCT05289570
terminated; "Terminated by new sponsor due to funding issues."
NCT05561140
terminated; "Emerging clinical data evaluated by Pfizer and shared with regulatory authorities indicates that the risk profile of voxelotor in people with SCD exceeds the benefits observed in previously generated global research and requires further…"
recorded 2026-09-01 · last checked 2026-09-04
Q6
Human studies of Voxelotor used Oxbryta® (voxelotor) 500mg Tablets — over how long?
studies of Voxelotor used the recorded amount. ClinicalTrials.gov · 2026-09-01
1 recorded entry; human; also "Oxbryta® (voxelotor) 500mg Tablets"
Show the evidence
humanNCT04930445
Oxbryta® (voxelotor) 500mg Tablets
recorded 2026-09-01 · last checked 2026-09-04
Q7
Voxelotor's half-life is 0-24 h — which schedules were studied?
0-24 h, the half-life Voxelotor's label states: "PK Parameter Voxelotor 1,500 mg Geometric Mean (%CV) Plasma PK AUC 0-24h (μg∙hr/mL) 278 (28.4) C max (µg/mL) 14 (24.5) Half-life (hours) 38.7 (30.2) Whole Blood PK AUC 0-24h (μg∙hr/mL) 3,830 (33.5) C max (µg/mL) 180 (31) In healthy subjects, voxelotor exposures were comparable when administered as tablet for oral…" DailyMed label · 3c557fac-29ec-483f-b691-8a935d4decc3 · 2023-12-26
tmax 2 hours.
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half lifepharmacokinetics
0-24 h; PK Parameter Voxelotor 1,500 mg Geometric Mean (%CV) Plasma PK AUC 0-24h (μg∙hr/mL) 278 (28.4) C max (µg/mL) 14 (24.5) Half-life (hours) 38.7 (30.2) Whole Blood PK AUC 0-24h (μg∙hr/mL) 3,830 (33.5) C max (µg/mL) 180 (31) In healthy subjects, voxelotor exposures were comparable when administered as tablet for oral suspension dispersed in water or as oral tablet swallowed whole.
tmaxpharmacokinetics
2 hours; Absorption The median plasma and whole blood T max of voxelotor after oral administration is 2 hours.
metabolismpharmacokinetics
The major route of elimination of voxelotor is by metabolism with subsequent excretion of metabolites into urine and feces.
recorded 2023-12-26 · last checked 2026-09-04
Q8
Which 2 trials of Voxelotor posted no result?
Posted no result
2 of 2 completed trials
Registrations
NCT04581356 and NCT04930328
Completion dates
oldest 2021-12-29; newest 2022-02-25
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Trial
NCT04581356
2021-12-29
NCT04930328
2022-02-25
Q9
At the median, Voxelotor's trials enrolled 44 people — anything larger?
Median enrolment
44
Largest enrolment
449
Registered trials counted
17
Q10
What do 361 spontaneous reports say about Voxelotor — and not say?
These are reports people sent to a regulator. They do not show the medicine caused the reaction. Nobody counted how many people took the medicine and reported nothing. The same event can be reported more than once, and many reports are incomplete. News coverage, lawsuits and new warnings change how often people report. A count is not a rate and not a risk.
Voxelotor appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 361 reaction mentions were counted: sickle cell anaemia with crisis 98; diarrhoea 94; nausea 52; headache 39. FAERS via Open Targets · CHEMBL4101807 · 2026-06-24
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sickle cell anaemia with crisis
98
diarrhoea
94
nausea
52
headache
39
rash
24
abdominal pain
16
4 more recorded rows
product dose omission issue
11
therapy non-responder
10
priapism
9
acute chest syndrome
8
recorded 2026-06-24 · last checked 2026-09-04
Q11
Which 10 reactions does Voxelotor's label not list?
• Sensitive CYP3A4 Substrates: Avoid coadministration of sensitive CYP3A4 substrates with a narrow therapeutic index.
drug_interactions
( 7.2 ) • Strong or moderate CYP3A4 Inducers: Avoid coadministration with strong or moderate CYP3A4 inducers.
drug_interactions
( 2.5 , 2.6 , 7.1 ) 7.1 Effect of Other Drugs on Voxelotor Strong or Moderate CYP3A4 Inducers Coadministration of strong or moderate CYP3A4 inducers may decrease voxelotor plasma and whole blood concentrations and may lead to reduced efficacy.
drug_interactions
Avoid coadministration of OXBRYTA with strong or moderate CYP3A4 inducers.
drug_interactions
Increase the OXBRYTA dosage when coadministration with a strong or moderate CYP3A4 inducer is unavoidable [see Dosage and Administration (2.5 , 2.6) and Clinical Pharmacology (12.3) ].
drug_interactions
7.2 Effect of Voxelotor on Other Drugs Voxelotor increased the systemic exposure of midazolam (a sensitive CYP3A4 substrate) [see Clinical Pharmacology (12.3) ].
2 more recorded rows
Interaction statementdrug_interactions
Avoid coadministration of OXBRYTA with sensitive CYP3A4 substrates with a narrow therapeutic index.
Interaction statementdrug_interactions
If concomitant use is unavoidable, consider dose reduction of the sensitive CYP3A4 substrate(s).
Where do the label and the trials disagree about Voxelotor?
"higher rate of vaso-occlusive crisis (severe pain caused by sickled red blood cells blocking blood flow and oxygen delivery to tissues) in patients with sickle cell disease receiving Oxbryta compared to placebo. There were also more deaths" against "approved": withdrawal status vs register status for Voxelotor.
OPEN_TARGETS_DRUG_WARNING, Drugs@FDA; 1 recorded pair
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OPEN_TARGETS_DRUG_WARNINGCHEMBL4101807
higher rate of vaso-occlusive crisis (severe pain caused by sickled red blood cells blocking blood flow and oxygen delivery to tissues) in patients with sickle cell disease receiving Oxbryta compared to placebo. There were also more deaths; 2026-06-24
Drugs@FDANDA213137
approved; 2026-08-28
Where it is registered
Where it’s registered
Withdrawn in United Kingdom; European Union; United States, 2024, for "higher rate of vaso-occlusive crisis (severe pain caused by sickled red blood cells blocking blood flow and oxygen delivery to tissues) in patients with sickle cell disease receiving Oxbryta compared…" (ChEMBL; Open Targets)
Withdrawn in United Kingdom; European Union; United States, 2024, for "vascular toxicity" (ChEMBL; Open Targets)
Withdrawn in United Kingdom; European Union; United States, 2024, for "unfavourable imbalance in the number of vaso-occlusive crises and fatal events" (ChEMBL; Open Targets)
Withdrawn in United Kingdom; European Union; United States, 2024, for "higher occurrence of vaso-occlusive crises (VOC) during treatment. Higher number of deaths" (ChEMBL; Open Targets)
ChEMBL 37 — CC BY-SA 3.0 Unported · ChEMBL ATC CC BY-SA · ClinicalTrials.gov — US Government work · Open Targets 26.06 — CC0 · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work
✗ required summary fields resolved: 4 required field(s) not terminal: Why people use it, Best-supported result, Biggest unanswered question, Human evidence
✓ public claims reviewed: 0 reviewed claim(s); drafts are never rendered
✓ source coverage passed: 7 source rows
✓ no critical contamination: no quarantine open
✓ canonical metadata passed: slug and display name present
✓ no raw internal fields: enforced by the copy-contract test over the rendered page
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